The present disclosure relates to an image reading device capable of reading image data from a document sheet, an image forming apparatus including an image reading device, and an adjustment value setting method implemented in an image reading device.
An image reading device mounted on a copier or the like may include a contact glass and an ADF (Auto Document Feeder), wherein a document sheet is placed on the contact glass, and the ADF conveys the document sheet. In this type of image reading device, two different reading methods are provided to read image data from the document sheet. Specifically, this type of image reading device can read image data from a document sheet placed on the contact glass. In addition, this type of image reading device can read image data from a document sheet when it is being conveyed by the ADF so as to pass a reading position on the contact glass.
Meanwhile, in this type of image reading device, a difference in density may occur between the image data read from the document sheet placed on the contact glass and the image data read from the document sheet conveyed by the ADF. For example, in the image reading device, in a case where image data is read from the document sheet placed on the contact glass, the document sheet is pressed against the contact glass by a cover member to be in close contact with the contact glass. On the other hand, in a case where image data is read from the document sheet conveyed by the ADF, the document sheet may be conveyed in a state of being separated from the contact glass at the reading position. In this case, a difference in the distance from the contact glass to the document sheet is generated between the case where image data is read from the document sheet placed on the contact glass, and the case where image data is read from the document sheet conveyed by the ADF. Due to the difference in the distance, the image data read from the document sheet conveyed by the ADF is denser (darker) than the image data read from the document sheet placed on the contact glass.
With regard to the above-described problem, there is known a conventional technology that can reduce the difference in image data density that occurs due to a difference between reading methods, by performing a shading correction using adjustment values that are obtained respectively for the reading methods in advance. Specifically, according to the conventional technology, an adjustment value is obtained for each of a plurality of reading methods based on image data read from a predetermined reference density document sheet by each reading method.